The purpose of this study is to correlate bone changes which have occurred in an animal study with the calculated stress patterns which exist in the cancellous bone. The emphasis of the study is to find the simplest usable stress-bone density relationship which predicts long term bone changes around total joint replacements, fracture fixation devices and osteotomies. In addition, detailed bone histormorphometry will be performed to see if the bone changes represent a stable equilibrium condition and to provide information on biological mechanisms which can be used to develop better theoretical models. The specific aims of this study are to: (1) measure the cancellous bone density throughout retrieved dog femora, both with and without implants in them; (2) perform sophisticated finite element stress analyses of the femora; and (3) perform a regression analysis between various stress parameters and bone density. Back scattered electron imaging and quantitative bone histomorphometry will be used to characterize the cancellous bone. A detailed 3-D finite element stress analysis will be used to determine the stress distributions.